Pressure control fill valves for pressurized dispensing containers are also known as Nickelson or Nicholson plugs. Pressurized dispensing containers typically comprise a volume for a fluid to be dispensed, such as a cream, lotion or solution, and a second, separate volume for a pressurized gas that is used to propel the fluid out of the dispensing container. When the gas is filled into its volume through an opening in the dispensing container, it is closed by inserting a plug or fill valve into the opening.
A pressure control fill valve or Nicholson plug, as described for example in U.S. Pat. No. 3,522,900, has an essentially cylindrical shape and comprises two circumferential grooves, which enable a dual-positioning of the plug within an opening. When positioned in a first position, flutes or cavities on the sidewall of the plug allow a gas to be passed through and into the container. When the plug is placed in its second position in the opening, the opening is fully sealed closed.
In case of extreme heat the propellant gas in such pressurized containers may become over-pressurized, and the container may explode. In order to prevent such hazard, fill valves or Nicholson plugs have been developed that allow a release of pressure in case of overpressure. They are used for applications with propellant gases that do not pose a threat to the environment. Such valve is disclosed for example in EP 1892198. The valve prevents over-pressurization of the gas container by leakage of over pressure gas while stopping the leakage once a given minimum pressure has been reached.
Such fill valves have the preferred ability to release overpressure. However, should the overpressure reach a certain high level or should the opening of the pressurized gas container enlarge as a result of a temperature increase, the fill valve will pop out of the opening entirely causing loss of the propellant gas and potential hazard to a user or person assembling the dispensing container.